Rail treatment method



R. E. FRICKEY RAIL TREATMENT METHOD Dec. 28, 1937.

Filed July 27, 19:56

FI.E E

R Y EN 0 WF w 1 A 4 Patented Dec. 28, 1937 UNITED STATES PATENT OFFICE RAIL TREATMENT METHOD Application July 27, 1936, Serial No. 92,715

4 Claims.

road rails, by heating the ends of the rails, fol-- lowed by a chilling operation. The rail ends so treated, provided a proper degree and pattern of 10 hardness is secured, are better able to withstand the battering action of rolling stock, which in untreated rail sections invariably causes rapid deterioration of rail joints. In carrying out such processes, one problem involved is that of securing 15 rapid heating of a localized layer of the rail ball. In applying such operations at rolling mills, it is evident that time is an important factor, not only with respect to the cost of such operation, but also to maintain a production rate commensurate with 20 the capacity of the mill. Likewise, it has been found that unless the heating iscarried outin such a manner as to produce uniform results in successive operations, it is diflicult, if not impossible, to secure a uniform degree of hardness. The present process and apparatus makes it possible to heat a localized layer of metal at the end of the rail-section in a minimum period of time, and with such uniformity that subsequent controlled chilling operations will produce a rela- 30 tively uniform degree of hardness.

- Another object of the invention is to provide a rail heating method and apparatus which is relatively simple and convenient to apply, and which is well adapted for use by rolling mills.

35 Further objects of theinvention -will appear from the following description in which the preferred embodiment of the invention has been set forth inadetail in conjunction with the accompanying drawing.

40 Referring to the drawing:

Fig. 3 illustrates a temperature-time curve, for

the type of heating which we employ.

50 Figs. 4 to 9 inclusive are cross-sectional views taken through a heated rail end. and showing the demarcation between metal heated to or above the critical temperature, and the remainder of the rail metal.

5;, The present invention makes use of means for producing an alternating magnetic flux, by use of an alternating current of more than standard I frequency, as for example a frequency of about 500 cycles. This flux is applied to the ball of a rail, at one end of a rail section, and in such a 6 manner that the major part of the flux is concentrated in an upper layer of the ball. The rail ball is heated by eddy currents and hysteresis, with the major part of the heat beinginitially generated in the upper layer of the ball, until this 10 layer attains the critical temperature at which it is no longer magnetic. Thereafter application of the flux is continued, and for reasons to be presently explained, the upper layer of metal is heated to a temperature level substantially above the critical temperature, as for example a temperature of about 1550 E, where the rail metal has a critical temperature of about 1350 F. The attainment of such a temperature level makes possible'a convenient time lapse between termination of the heating operation and the beginning of the chilling and quenching operation, and it also makes the entire process less critical, and thus facilitates the production of uniform results.

Referring now to the drawing, I have shown 26 what can be termed a transformer I 0, and which consists of an inverted U-shaped magnetic core H, the side legs of which are provided with windings l2. It is desirable to form the windings of metal tubing l3, which can be embedded in a 30 suitable refractory cement. In operation, cooling water or other suitable cooling fluid, is circulated through the windings, in order to maintain the various parts of the transformer below such temperature values as might cause failure. The end portions ll of the core are shown provided with oppositely bevelled faces l6, adapted to engage the upper side edgesof the rail ball ll.

The exciting circuit for the transformer Ill can include an alternating current generator l8, delivering alternating current at a frequency of say 500 cycles per second, and capable of supplying a relatively large amount of electrical power, as for example from 15 to 25 kilowatts. In order to assist an operator in checking operation of the transformer, the circuit is also shown including a volt meter l9, a watt-hour meter 2|, and an ammeter 22. Also a condenser 23 is shown shunted across the windings of the transformer III, in order to bring the power factor as near as possible to unity.

Use of the equipment described above, and the .carrying out of the present invention, can be described as follows:-Assuming that the ends of 131 pound rails are to be heated, the electrical power input to the transformer l0 can be about 18 kilowatts. The ends of the transformer core are seated upon the rail ball, in the manner illustrated in Figs. 1 and 2. Thus the core is contacted with the upper part of the rail ball along two spaced lines, whereby the major part of the flux enters and leaves the rail along narrow zones located in the regions where the upper surface 24 of the rail ball merges with the side ball faces 26. The length of these zones will of course depend upon the dimensioning of the core ends ll, although with a 131 pound rail, 2, length extending about three inches from the end of the rail, will sufllce. It will be evident that heat insulating material can be interposed between the ,core and the rail, to minimize transfer of heat into the core.

.Current from the generator [8 is now applied to the transformer windings, to cause alternating magnetic flux to thread laterally across the rail ball. While the entire rail ball forms a magnetic path through which the alternating flux traverses, the flux density is by far greatest in the upper layer of the rail ball, since this upper layer forms the shortest. path between the pole ends it. Because of this greater flux density, and also because of so-called skin effect, a greater amount of heat is developed in this upper zone of the ball, including heating by virtue of flow of eddy currents, and heating by hysteresis loss. Thus the upper portion of the rail ball is rapidly heated to the so-called critical temperature, at which the steel of the rail no longer is magnetic.

The magnetic flux now becomes denser in the lower portions of the rail ball, underlying the portions which have been heated to the critical temperature, and although the flux density in the upper layer of heated metal is greatly reduced,

'heat in this upper layer continues to be generated, by virtue of flow of eddy "currents through the same. Thus with apparatus capable of maintaining the total amount of magnetic flux substantially constant throughout a heating period, it is possible to carry the temperature of the upper ball portion to a value considerably above the critical temperature, while the underlying portion of the ball remains magnetic.

After a given period of time, such a period of about 80 seconds for the representative example cited above, the upper layer of metal will have attained a temperature in the neighborhood of 1550" F. The transformer is then removed, and the upper surface of the rail end is chilled in a manner calculated to produce a predetermined degree of hardness. For example the upper surface of the rail end can be contacted with a chilling liquid like water, applied at the end of a predetermined interval following discontinuance of. heating, and with other factors controlled in such a manner as to produce absorption of a predetermined amount of heat.

The curves of Fig. 3 serve to illustrate how my method differs from other induction heating methods employing a circuit of magnetic material. Curve a represents a typical induction heating of a mass of steel in a circuit of mag-' netic material, where a magnetic flux is threaded relatively uniformly throughout the body. It

, will be noted thatthe temperature rapidly rises to the critical value at about 1350 F., and thereafter the temperature-time curve flattens out, showing that there is no further increase in temperature. While it is possible to harden steel heated to atemperature of 1350 F., any such process will be highly criti al, due to the fact that a slight lowering of the temperature below such value before the chilling operation, will cause a wide variation in the degree of hardness pro duced. The type of heating which I utilize is illustrated by curve I), which changes its slope at the critical temperature, but which shows a continued rise in temperature as the heating operation is continued. This curve b was plotted with an electrical input of about 18 kilowatts, and with a temperature being measured at a point about A inch below the upper surface of the rail ball, near the end of the rail being heated. It will be noted in connection with this curve that the critical temperature was reached in about seconds following commencement of the heating operation, and that in about 100 seconds the curve reached an elevated temperature of about 1590 F., and commenced to flatten out, showing that a further extension of the heating period would not be productive of a materially higher temperature. I am of the opinion that the successful features of my method can be attributed.

largely to the discovery of a proper procedure to carry the temperature of the upper surface of the rail beyond the critical value, as exemplified sequent figures represent transverse sections taken at consecutive positions extending back from the end of the rail, and spaced one-half inch apart. Note that for a substantial distance back from the end of the rail, an upper layer of metal is provided which is heated to or above the critical temperature. It will also be evident from these figures that chilling can be carried out to harden the side faces of the ball as well as the upper surface, or to harden only a limited zone in the upper surface of the ball.

' Previous mention has been made of the desirability of controlling both the heating and chilling operations, to produce uniformity in successive hardening operations. With the type of heating described, it has been found possible to successively heat rail ends within remarkable close limits, as for example the limits of plus and minus 10 F. In practice, the generator I 8 is constructed and operated to produce a fairly constant output. From the time current is applied to the transformer ID, the operator determines the end of the heating period by observing' the watt-hour meter 2|, or this watt-hour meter can be provided with an automatic means,

whereby after a predetermined amount of energy tion of heat, as for example by causing a stream of the chilling liquid to flow over the heated surface of the rail at a predetermined velocity.

heat said layer to a temperature corresponding to the critical temperature of the rail metal, and

thereafter continuing to heat said layer to a temperature materially above said critical temperature value by causing the major portion of said flux to pass through lower magnetic strata of the rail ball.

2. In a method of heating steel rail ends preparatory to hardening the same by chilling, placing an upper layer of the rail ball at one end of the rail in a magnetic flux path, causing an alternating magnetic flux to'thread said path to inductively heat said layer to a temperature corresponding to the critical temperature of the rail metal, said magnetic flux entering and leaving the rail ball at spaced zones located at the upper side edges of the rail ball, and thereafter continuing application of said alternating magnetic flux to thereby continually heat said layer to a temperature materially above said critical temperature value, with passage of a major part of the magnetic flux through progressively lower magnetic strata of the rail ball.

3. In a method of heating steel rail ends preparatory to hardening the same by chilling, placing an upper layer oi the rail ball, at one end of the rail, in a magnetic flux path, causing an alternating magnetic flux to thread said path to heat said layer to a temperature corresponding to the critical temperature of the rail metal, thereafter continuing to heat said layer to a temperature materially above said critical temperature value by causing the major portion of said flu'x to pass through progressively lower strata of the rail ball, and discontinuing the passage of magnetic flux aftera predetermined amount of electrical energy has been consumed.

4. In a method of heating steel rail ends preparatory to hardening the same by chilling, placing an upper layer of the rail ball, at one end of the rail, in a magnetic flux path, the pathextending laterally across the rail between the upper parallel side edges of the rail ball, causing an alternating magnetic flux to thread said path to heat said layer to a temperature corresponding to the critical temperature or the rail metal, the major part or the flux entering and leaving said rail along narrow zones substantially coincident with said side edges, and thereafter continuing to subject the rail ball to said magnetic flux without a material shift in said zones, to heat the upper layer to aternperature materially substantially above said critical temperature.

ROYAL E. FRICKEY. 

